It relates more particularly to float and variable resistance devices using the bottom of the tank as a reference level and of the the comprising:
a base for fixing to a wall of he tank;
a support hinged about a horizontal axis to the portion of the base inside the tank;
a shoe carried at the bottom end of the support so that the shoe rests against the bottom of the tank;
a resistor element carried by he support;
a float carried by an arm which is hinged about a non-vertical axis to the support to track the level of fuel; and
a cursor carried by the arm and engaging the resistor element to define a resistance which varies as a function of the level of liquid contained n the tank.
Such devices are described, for example, in patent documents U.S. Pat. No. 3,925,747, U.S. Pat. No. 3,449,95, and DE-C-3310704.
These devices may be called "bottom reference" devices.
Insofar as the support carrying the resistor element is urged to bear against the bottom of the tank, these bottom reference devices improve measurement accuracy over prior systems where the resistor element support is rigidly mounted on he wall of the tank.
However, the Applicant has determined that if additional precautions are not taken concerning the shape of the shoe, such prior bottom reference systems give rise to a small error which may be serious when measuring a minimum reserve quantity in the tank.
The object of the present invention is to improve devices of the above-specified type by improving their accuracy so that regardless of the position o the bottom o the tank due to possible deformation, the device o the present invention always provides the same "tank empty" signal when the level of fuel corresponds o the same minimum measurable depth above the bottom.